1. Field of the Invention
The present invention relates to a room temperature curable organopolysiloxane composition, and more particularly to a room temperature curable organopolysiloxane composition useful as building sealing materials and the like.
2. Description of the Prior Art
In a filling application to the joint portions of concretes and sashes, the peripheral portions of glasses, and the like, there are generally used sealing materials such as synthetic rubbers. Conventionally known sealing materials include various materials, such as silicones, polysulfides, polyurethanes, acryl resins, SBR, and butyl rubbers, among which silicone sealing materials are widely used from the view point of excellent adhesion, resistance to heat and weatherability, and durability. The silicone sealing material, which is generally charged in a cartridge, is filled in portions to be applied, such as joints, and the filled portions are surface-finished with a spatula or the like, followed by curing. In that case, the sealing material is required to have non-flowability and good application workability. In order to satisfactorily improve the non-flowability and the application workability, it is necessary to add a large amount of silica fillers and to blend the resulting composition. However, since a blender used undertakes a very large load when blending, it brings the disadvantages that productivity decreases, that in an extreme case, the production comes to be impossible, and that the characteristics of a cured sealing material obtained by curing become poor. Also, there is known a silicone rubber composition to which boric acid or alkyl borate has been added in order to improve the flowability of a silicone composition [Japanese Patent Publication (kokoku) No. 39-22438]. This composition, however, has the drawbacks that a satisfactory effect can not be obtained unless the composition is heat-treated, and that its curing reaction may be inhibited.
Further, there is known a silicone rubber composition prepared by adding to a composition made up of a liquid organopolysiloxane and a hydrophobic silica, an organic liquid having a vapor pressure equal to or more than a specific value [Japanese Patent Publication (kokoku) No. 49-5510]. However, this composition is disadvantageous in that the organic liquid used has flammability, volatility or toxity.
Furthermore, there is known a method for improving the flowability of a silicone rubber composition by adding a polyether composition to a silicone rubber. However, the silicone rubber composition obtained by this method has the drawbacks that the composition can not be readily applied. Especially when surface-finishing is performed with a spatula, the spatula can be detached with difficulty, causing stringing.